/Engine/Source/Runtime/CoreUObject/Public/UObject/SparseDelegate.h
Sparse delegates can be used for infrequently bound dynamic delegates so that the object uses only 1 byte of storage instead of having the full overhead of the delegate invocation list. The cost to invoke, add, remove, etc. from the delegate is higher than using the delegate directly and thus the memory savings benefit should be traded off against the frequency with which you would expect the delegate to be bound.Helper class for handling sparse delegate bindings
struct FSparseDelegateStorage